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Results show that 3-chlorocatechol degradation follows a dechlorination or dehalogenation step catalyzed by a muconolactone isomerase-related enzyme by Rhodococcus opacus 1CP. Data also point out to a genetic background for the degradation pathway.

Research has been conducted on the monofluorophenols. Results demonstrate that fluoropyrogallols are involved in the monofluorophenol biotransformation in Rhodococcus opacus 1cp.

A study was conducted to describe the gene macA encoding the microbial enzyme maleylacetate reductases, in the degradation of chlorocatechols or 5-chlorohydroxyquinol through an analysis of cloned chloroaromatic compound-utilizing proteobacteria, such as the chlorophenol-degrading strain Rhodococcus opacus. Genetic encodings of maleylacetate reductases were found in specialized chlorocatechol gene clusters. Analysis showed that maleylacetate reductase macA in R opacus was not a part of the gene cluster.

Cloning and sequence analyses were performed on a DNA fragment from Rhodococcus opacus, which comprised the gene for the 3-oxoadipate enol-lactone-hydrolyzing enzyme of strain 1CP. The results revealed that the gene was part of a protocatechuate catabolic gene cluster. The gene was also found to be connected to the pcaC gene, which codes for a different 4-carboxymuconolactone decarboxylase in proteobacteria. Moreover, the transcription of the pcal, coding for a subgroup of succinyl-CoA:3-oxoadipate CoA-transferase, was divergent from pcaH.

Polymerase chain reaction with primers obtained from sequences of N termini and peptides of purified chlorocatechol 1,2-dioxygenase and chloromuconate cycloisomerase was used to clone the chlorocatechol catabolic enzymes from Rhodococcus opacus 1CP. Sequencing analysis showed that the clones were from different areas of the same gene cluster. The results further revealed that the transcription of clcB gene for chloromuconate was divergent from a gene coding a LysR-type regulatory protein.

A fragment of the Rhodococcus erythropolis 1CP catechol gene cluster was cloned and sequenced to characterize the pathways of catechol and chlorocatechol catabolism. DNA sequence analysis of the Rhodococcus erythropolis 1CP muconate cycloisomerase-encoding region indicated the presence of five open reading frames. However, the cloned DNA did not contain the complete catA gene for catechol 1,2-dioxygenase. Furthermore, the catechol 1,2-dioxygenase of the microbe was similar to the chlorocatechol dioxygenases of gram-negative strains.

Standard procedures enable the purification of 6-chlorohydroxyquinol 1,2-dioxygenase from 2,4,6-trichlorophenol-grown cells of Streptomyces rochei 303. A comparative study of enzymatic activity of the S. rochei enzyme with that of Azotobacter sp. strain GP1 reveals that S. rochei enzyme prefers 6-chlorohydroxyquinol over hydroxyquinol. Sequence analysis reveals significant similarity between these enzymes in the NH2-terminal amino acid sequences. The enzyme has 1 mol of iron per mol of enzyme and contains of two identical 31-kDa subunits.

Research has been conducted on 1,2-dioxygenase, chloromuconolactone dehalogenase and chloromuconate cycloisomerase from Rhodococcus opacus 1cp grown on 2-chlorophenol. Results demonstrate that 2-fluoromuconate can be converted to 5-fluoromuconolactone by chloromuconate cycloisomerase, and that 5-fluoromuconolactone can be dehalogenated to cis-dienelactone by chloromuconolactone dehalogenase.

This work was aimed at studying the response of soil non-spore-forming actinobacterial strainArthrobacter agilisLush 13 to changing natural conditions, such as nutrient availability and the presence of degradable and recalcitrant aliphatic and aromatic substrates. TheA. agilisstrain Lush13 was able to degrade octane, nonane, hexadecane, benzoate, phenol, and 2,3-, 2,4-, 2,5-, 2,6-dichlorophenols, but not grew on 3,4-dichlorophenol, 2,3,4-, 2,4,5-, 2,4,6-trichlorophenol (TCP), pentachlorophenol (PCP), 2-chlorobenzoate, 3-chlorobenzoate, 3,5-dichlorobenzoate, 2,4-dichlorobenzoate. Under growth-arresting conditions due to nitrogen- or multiple starvation or recalcitrant (non-utilizable) carbon source, the studied strain preserved viability for prolonged periods (4–24 months) due to transition to dormancy in the form of conglomerated small and ultrasmall cyst-like dormant cells (CLC). Dormant cells were shown to germinate rapidly (30 min or later) after removal of starvation stress, and this process was followed by breakdown of conglomerates with the eliberation and further division of small multiple actively growing daughter cells. Results of this study shed some light to adaptive capabilities of soil arthrobacters in pure and polluted environments. [ABSTRACT FROM PUBLISHER]

The process of benzoate degradation by strainRhodococcus opacus1CP after a five-year dormancy was investigated and its peculiarities were revealed. The strain was shown to be capable of growth on benzoate at a concentration of up to 10 g L−1. The substrate specificity of benzoate dioxygenase (BDO) during the culture growth on a medium with a low (200–250 mg L−1) and high (4 g L−1) concentration of benzoate was assessed. BDO ofR. opacus1CP was shown to be an extremely narrow specificity enzyme. Out of 31 substituted benzoates, only with one, 3-chlorobenzoate, its activity was higher than 9% of that of benzoate. Two dioxygenases, catechol 1,2-dioxygenase (Cat 1,2-DO) and protocatechuate 3,4-dioxygenase (PCA 3,4-DO), were identified in a cell-free extract, purified and characterized. The substrate specificity of Cat 1,2-DO isolated from cells of strain 1CP after the dormancy was found to differ significantly from that of Cat 1,2-DO isolated earlier from cells of this strain grown on benzoate. By its substrate specificity, the described Cat 1,2-DO was close to the Cat 1,2-DO from strain 1CP grown on 4-methylbenzoate. Neither activity nor inhibition by protocatechuate was observed during the reaction of Cat 1,2-DO with catechol, and catechol had no inhibitory effect on the reaction of PCA 3,4-DO with protocatechuate. [ABSTRACT FROM AUTHOR]